Current therapies to treat opportunistic infections associated with AIDS are either highly toxic, extremely expensive or marginally effective. In addition, there is no therapy recognized as effective for certain of the pathogens. Because present therapies produce toxic reactions in a large percentage of patients, the availability of alternative (or new) therapeutics is of upmost importance. Since these infections produce significant morbidity and mortality in patients with AIDS, the National Institute of Allergy and Infectious Diseases (NIAID) has funded several programs to facilitate drug development efforts against opportunistic infections by providing contract resources for efficacy evaluations in animals, a critical component in new drug approval. The availability of animal model testing systems will provide the NIAID with testing capabilities to evaluate therapies for treatment against Mycobacterium avium, both singly and in combination. This will permit the submission of the resulting data in support of an IND application for the new therapy. The contractor will have the capability to evaluate agents in small animals (in vivo) and culture (in vitro) model testing systems; develop alternative protocols to accommodate special characteristics of individual therapies or model test systems; determine optimal dosages, routes, and schedules of agent administration, etc, to assist the sponsor in the development of new therapies against M. avium.